Lubricating oil



Patented Apr. 26, 1932 UNITED STATES PATENT OFFICE JACK ROBINSON, OF WOOD RIVER, ILLINOIS, ASSIGNOR TO STANDARD OIL COMPANY,

OF WHITING, INDIANA, A CORPORATION OF INDIANA LUBRIGATING OIL No Drawing. Application filed June 30,

This invention relates to lubricating oils and particularly to oils for lubricating turbines and similar purposes.

When ordinary'lubricating oils are used in steam turbines, they readily form objectionable quantities of sludge. In order to avoid this objectionable characteristic, it has become the practice to employ as turbine oils, lubricating oils which have been drastically treated with strong or fuming sulphuric acid to remove coloring matter and large percentages of other constituents, to give a socalled white oil. These highly treated oils are, however, subject to the further disadvantage that, after a relatively short period of use, they form acidic oxidation products and form emulsions from which the oil is separable only with difficulty.

The basis of the present invention is the discovery that by subjecting the lubricating oil to treatment with a certain, relatively small, critical amount of sulphuric acid, a much more satisfactory turbine oil possessing much greater resistance to oxidation and retaining great demulsibility, results.

As stated, the amount of the acid used for the treatment is critical and will vary for various oils, the nature of the acid employed and other factors. Accordingly, the invention will be described by reference to a particular oil and particular tests will be described, by means of which, the critical treatment for any particular oil may be determined. j j

For this purpose the following specific example is given.

Fifteen gallons of mid-continent distillate lubricating oil of 296 seconds viscosity at 100 F. are mixed with five gallons of a similar distillate of 100 seconds viscosityat 100 F. to give a mixture of 235 seconds v1scosity at 100 F. A half pound of fuming acid per gallon of the original charge isapplied at intervals of twenty-four hours, and the batch given an air blow of from twenty to one hundred minutes. The batch is allowed to settle over night and the sludge withdrawn. The acid supplied each day is based upon the original oil treated, disregarding treating losses but taking into 1927. Serial No. 202,758.

account the samples removed daily. This is continued for eleven dumps so that the amount of fuming acid supplied is 5 pounds per gallon of the original oil. The sludge loss during this period amounts to about 65% of the original oil. About 15% loss is incurred after the first dump, about 8% after each of the second andthird dumps, about 6 after each of the fourth and fifth dumps, and about 4 after each of the sixth and seventh dumps.

Each sample withdrawn is blown for about one hour at a temperature of between 140 and 160 F. The sour oil is neutralized with caustic soda in excess and kept at 160 F., the caustic soda is withdrawn, and the oil given two alcohol washes and a water wash followed by blowing until free from water. The sample is then filtered through clay, and subjected to an oxidation test.

The method of conducting this test is to subject a sample of the oil to oxidation conditions which simulate as far as possible the oxidation conditions to which turbine oil is subjected during use and to determine the acidity and demulsibility (Herschel) after a certain time. I

A suitable oxidation test is to pass oxygen through a sample of the oil maintained at about 212 F. for a long period. It has been found that the oxidation ordinarily has a slight effect at first, but that the rate of oxidation increases rapidly with time. p A suitabe period of time in which the course of ox-v idation is shown unmistakably is about three hundred hours. I

The following results have been obtained:

' gg .Qemulsibil- Fuming acidpounkls per gallon pier gaLgafO g g fig 01 a or hrstest 300hrs. test The demulsibility test employed in testing the above samples was the (Herschel) test No. 320.31 described Technical Paper (323b), Bureau of Mines, 1927, on' page 85. This test is made ata temperature of 130 F. with 27 cc. sample and the basis for determining the maximum rate of demulsibility is one hour. Thus, the maximum possible demulsibility is 1620.

It is remarkable that the oil treated with 4.5 and 5.5 pounds of acid per gallon develops large aeidities and that immediately below this point, that is, oil treated with two or three pounds of acid per gallon, practically no acidity develops. As to demulsibility, in the presence of the large amounts of acid produced in the oils treated with 4.5 and 5.5 pounds per gallon, soaps would form with the metal of the turbine and reduce the demulsibility of these oils greatly below the figures shown above; for example the demulsibility would be reduced substantially below 150 under these circumstances.

3.5, specific 'example'thereof, it is notintended that such details shall be regarded as limitations upon the scope of the invention, except in so far as included in the'accompanying claims. In particular, it is pointed out 46 that it is impossible to state definitely the extent of the critical amount of acid necessary for treatmentof different oils under different conditions. Applicant has, however discovered that there is a certain critical amount of acid which yieds oils of remarkable properties and utility, and has clearly shown how such critical amount may bedetermined for any'particular oil. It is to be understood that the expression critical amount used in the appended claims is intended to designate that particular amount of acid which yields oils which are strongly "resistant to oxidation and retain high demulsibility after treatment to turbine operation oxidation conditions, for prolonged periods, such as are exemplified by the oils described above which have been treated with two or three pounds of fuming sulphuric acid per gallon. o

Iclaim: r

1. The method of producing turbine oils which consists in subjecting lubricating oils to treatment with a critical amount of sulphuric acid of a strength at least equal to that of concentrated sulfuric acid, calculated to render it remarkably resistant to oxidation 'demulsibility whensubjected to turbine oxiand retain high demulsibility when subjected to turbine oxidation conditions for a prolonged period.

2. The method of producing turbine oils which consists in subjecting a lubricating oil 'fu'ric acid, finishing said samples,'and subjecting them for a long period to oxidation treatment resembling the conditions in an operating turbine, determining the acidity and demulsibility of the oxidized samples, and treating the bulk of the oil with the amount of said sulfuric acid which corresponds with the amount of said sulfuric acid used in the treatment of a sample which gives a low acidity and high demulsibility after said oxidation test. p 7

3. The method of producing turbine oils which consists in subjecting a lubricating oil to a treatment with fuming sulphuric acid-to the extent of about two to three pounds per gallon to render it remarkably resistant to oxidation and retain high demulsibility when subjected to turbineoxidation conditions foraprolonged period.

4c. The method of producing turbine oils 7 which consists in subjecting a lubricating oil to repeated treatments with fuming sulfuric acid, taking samples of the oil treated with difi'erentamounts of fuming sulfuric :acid, finishing said samples, and subjecting them for a long period to oxidation treatment "re- 'sembling the conditions in anoperatingturbine, determining the acidity and demulsibility of the oxidized sa mples, 'and treating the bulk of the oil with the amount of fuming sulfuric acid which corresponds with the amount of fuming sulfuric acidused-in the treatment of a sample which gives a low acidity and high demulsibility after said oxidation test. s i

5. The method, of which consists in treating various samples of a given bulk of lubricating oilwithvarious amounts of fuming sulfuric acid to deter producing turbine oils mine the critical amount of sulphuric acid g calculated to render itrema rkably resistant to oxidation and retain high 'demulsibility when subjected to turbine oxidation condi-' tions for a prolonged period, and treating cal amount of fuming sulfuric acid so determined.

6. The method of producing turbine oils which consists in subjecting a lubricating oil to a treatment with sulphuric acid. of av strength atleast equal to that of concentrated sulfuric acid to the extent of about two-to three pounds per gallon to render it remarkthe bulk of the lubricating oil with the critiably resistant to oxidation and-retain high dation conditions for a prolonged period,

7 The method of producing turbine oils which consists in treating various samples of a given bulk of lubricating oil with various amounts of sulphuric acid of a strength at least equal to that of concentrated sulfuric 

